$($c$)$ Recently, in vivo testing has shown that the substituted $1,4-$dihydropyridine $F$ shown below has anticonvulsant activity. It can be prepared using the Hantzsch synthesis.

$($i$)$ Show the starting materials that would be required to prepare $F$ using a Hantzsch synthesis. $[3$ marks$]$

$($ii$)$ Summarise the three main stages involved in the overall reaction.

$[3$ marks$]$

$($iii$)$ Draw out a mechanism for ONE of these three stages. Ensure that you also provide a short written description of the mechanism you have drawn.

$[9$ marks$]$

F